Sapphire is widely used material for blue emitting diode, laser diode devices, visible-infrared window and radome applications. Although there is a large mismatch in the lattice constants and thermal expansion coefficient between nitride and sapphire, sapphire is still known as the most commonly used substrate in the GaN device for its physical robustness and high temperature stability. The ensuing component performance is highly dependent on the quality of the surface processing. In this work the effects of mechanical polishing, chemo-mechanical polishing (CMP) as well as CMP and subsequent chemical etching on the properties of sapphire substrate surfaces has been studied. The sapphire substrates have been investigated by means of polarizing microscopy, atomic force microscopy (AFM), X-ray diffraction rocking curves (XRCs) and micro-Raman spectroscopy. The results show that CMP with subsequent chemically etching yields the best quality sapphire substrate surfaces. The optimized conditions to realize good substrate and smoother surface morphology have been obtained.